Stainless Steel vs. Aluminum: Which is Better?

Stainless steel and aluminum are two metals very important to the foodservice industry. So which is better? Both, actually. Each metal is better for different applications. When we attended Vollrath University in late June, they broke the two down and explained which is better for specific uses.

Stainless Steel

Introduction

Stainless steel is made up of iron, chromium, nickel, manganese and copper. This iron alloy has a minimum of 10.5 percent chromium, an agent that provides corrosion resistance. It’s non-porous and non-corrosive with a higher resistance to rust as well.

What makes stainless steel less corrosive is a “passive” layer of chromium oxide that the chromium forms.

Vollrath explained this is 12 to 30 percent chromium and too thin to be visible but protects the metal beneath. Nickel assists in the process and restores itself with oxygen. So—as long as the passive layer or film stays intact, isn’t broken or contaminated, a product remains stainless.

Can it still stain though? Yes. A scratch to the surface can lead to rust. So can heated water that leaves deposits and chlorides found in salt, water, cleaner and quaternary salts. But even though the possibility to stain is there, Vollrath reminded us it’s called stainless because it won’t rust, corrode or rust as easily as ordinary steel.

Types of Stainless Steel

There have been at least 150 grades of stainless steel found; 15 of those are used in the foodservice industry and four of those 15 are more popular among foodservice equipment and supplies.

Vollrath explained there are two types of stainless steels:

Austenitic

Comprised of alloy with nickel and chromium. There are the 200 and 300 series stainless steels and are the most specified grades in foodservice. Austenitic stainless steels are corrosion and water resistant. They are non-magnetic as well.

200 series: In general, this type of stainless steel is commonly used for wheel covers and door hardware. Being more specific to the foodservice industry, these are commonly found in counters, oven parts, covers and tray slides.

300 series: These are typically found in steam table pans, sinks, food processing equipment and Bain Maries. The 300 series contains 301 and 304 stainless steels.

301 stainless steel is 17 percent chromium and 6 percent nickel (otherwise known as 17/6). As there is less nickel, it isn’t as corrosion resistant as 304, however Vollrath said it is more difficult to form and is stronger because it has less nickel.

304 stainless steel is 18 percent chromium and 8 percent nickel (otherwise known as 18/8). It resists most oxidizing acids and is very corrosion resistant.

Ferritic

This type of stainless steel does not contain nickel and does not have the same corrosion resistance found in the 200 and 300 stainless steels. It’s also magnetic.

400 series: In general, type 430 stainless steel (explained more in detail below) is found in automotive trim, architecture and mufflers. Specific to the foodservice industry, this type is common in flatware, carts, structural parts and steam tables.

430 stainless steel is 16 to 18 percent chromium and contains no nickel (otherwise known as 16/18-0). Despite not having any nickel, it is quite corrosion resistant but not as much as the 300 series.

Aluminum

Introduction

Vollrath explained aluminum has higher oxidation and corrosion resistance because of passivisation. When aluminum is oxidized, its surface will turn white and will sometimes pit in some extreme acidic or base environments.

Aluminum is more lightweight than other metals and is strong. It’s particularly strong when blended with alloy elements, hence being ideal for structural parts and equipment housings as well as heavy gauge cookware.

Aluminum is also a great conductor of heat. Vollrath said it has excellent thermal conductivity which makes it ideal for cookware and equipment where good heat conductivity is needed. It is also less expensive than stainless steel.

Types of Aluminum

Similar to stainless steel, there are different types of aluminum, each different for specific foodservice applications.

1100

Vollrath said this type of aluminum is 99 percent pure. It’s soft, forms easily and can’t withstand tough commercial duty applications or high heat applications without warping. This type of aluminum also dents and scratches easily.

3003

This type of aluminum is one to 1.5 percent manganese. It forms easily and items of this type hold up extremely well for normal use, however, may still be too soft for commercial/heavy duty use.

3004

This type of aluminum is one to 1.5 percent manganese and 1 percent magnesium. It’s more difficult to form than the 1100 or 3003 and Vollrath said is much more impervious to sever use. It’s tougher and lasts much longer than 3003. This is a type of aluminum ideal for quality cookware, bake ware and tougher commercial equipment applications.

Recap: Stainless Steel vs. Aluminum…Which is Better?

Vollrath wrapped up this section with the following information to help determine which metal is best for specific applications.

Strength

Stainless steels are harder and are especially harder to form than aluminum.

Thermal Conductivity

Aluminum has a much better thermal conductivity than stainless steel.

Cleaning

Aluminum is more porous and prone to surface scratches and dent, which makes it harder to clean.

Effect of Foods

Stainless steel is less reactive with foods. Aluminum can react to foods which may affect color and flavor.

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